A: Yes, as long as the Keeper is compatible with the Creeper. Some attaching Creepers can only attach to Keepers with certain specific qualities, like they have to be sentient, or they have to be investigators, or they have to be mechanical.
For example, you could attach both Evil and Malfunction to the Teleporter to get an Evil Malfunctioning Teleporter. In Cthulhu Fluxx, The Poet could be Mad and also have Nightmares… heck, he could also be Metamorphosed as well.
This can make it easier to get rid of those Creepers, since you only have to get rid of that one VERY afflicted Keeper to ditch ALL the attached Creepers.